In order to facilitate communication between computing devices, data may be transmitted between devices in a format that is comprehensible by both the sending and receiving devices. In this regard, protocols have been developed that enable communication between computing devices connected by way of a network or the Internet. These protocols provide a standardized format in which data may be sent over a network. Accordingly, data may be sent between computing devices on a network or over the Internet and be properly interpreted by the receiving computer. The most common set of protocols governing communication over or between networks is the Internet Protocol Suite (commonly referred to as TCP/IP).
The Internet Protocol Suite includes several layers that provide different functions at different levels of abstraction. These layers consist of the Application layer, the Transport layer, the Internet layer, and the Link layer. Within each of these layers, different protocols have been developed to facilitate communication between computing devices. For instance, within the Transport layer many protocols have been developed in order to format data for communication over a network such that the sending and receiving computer devices may properly direct the data to and from an appropriate application on each computer. These protocols may provide different features depending upon the nature and intended role of the protocol. For example, connection-oriented data stream support, reliability, flow-control, and error correction may be provided by protocols within the Transport layer. However, the feature set for each protocol may be different and may include or omit features to strike a balance between performance (e.g., data transfer rates) and reliability (e.g., data integrity at the receiving device). That is, a protocol tailored for high rates of data transfer generally includes fewer data reliability features, whereas protocols tailored for high reliability may include reliability features that may limit data transfer rates. Two popular and widely used transport layer protocols demonstrate this inherent balance between performance and reliability. These are the Transport Control Protocol (TCP) and the User Datagram Protocol (UDP).
TCP connections provide data transfers that help to ensure high data integrity at the receiving device, but generally provide slower data transfer speeds than speeds obtainable using a UDP connection. A TCP connection utilizes a positive acknowledgement with retransmission technique that requires an acknowledgment message to be exchanged between a receiving entity and a sending entity to confirm that each individual data packet sent from a sender to a receiver was in fact received at the receiver. If not received, the data packet is retransmitted until acknowledgement is received from the receiver. While this may help to ensure that the data being sent arrives in the correct order and may assist in ensuring data packet delivery, the high reliability of the TCP connection comes at a cost of speed. The acknowledgement messages exchanged between sender and receiver take time to transmit. In turn, these messages are exchanged during times that could otherwise be used for transferring data, thus limiting the overall transfer rate. For example, oftentimes delays in the order of seconds are required waiting for out of order messages or waiting for retransmission of a packet.
A UDP connection, on the other hand, provides high speed data exchange, yet may sacrifice features that help ensure the integrity of data received at a receiving entity. In this regard, data packets (i.e., datagrams) sent via a UDP connection are not subjected to acknowledgement or other integrity checks similar to those present in a TCP connection. Thus, the transfer rate of a UDP connection may be higher than that of a TCP connection. However, there may be no mechanism in a UDP connection to help ensure that the all data packets were received, that all data packets arrived in order, and that there was no corruption of data during the transfer. Rather, data is simply delivered to the Application layer in the form it was received. As such, UDP connections either rely on applications to perform integrity checks, or assume that such integrity is of lesser importance than the overall speed of data transport. In this regard UDP connections are valuable in certain applications such as Internet broadcasting, voice-over-IP (VoIP) transmissions, queries to the Domain Name System (DNS), streaming media applications such as IPTV, Trivial File Transfer Protocol (TFTP), online gaming, or other time sensitive communications where a loss in data integrity is preferable to a slow communication due to the time sensitive nature of the data.
In short, a UDP connection emphasizes speed at the cost of reliability, while a TCP connection emphasizes reliability at the cost of speed.
Other protocols been developed for data exchange that are tailored for particular applications. One example of such a tailored protocol is the BitTorrent protocol. BitTorrent allows for exchange of a relatively large amount of data without dominating the bandwidth of any one computing device participating in the data transfer. In this regard, a torrent file is obtained by a receiving computer that in turn uses the file to seek and download small portions of a target file from various locations in the network (often called seeds). In this regard, the torrent file directs the acquisition of data from a multitude of different sources. However, BitTorrent was developed in order to provide relatively low bandwidth usage which is spread across a large number of users in the network in order to transfer data. Additionally, transfers using the BitTorrent protocol may use existing transport protocols (e.g. TCP), and are thus subject to the limitations presented by such transport protocols. As such, the data transfer is often slow as the usage of any one user's bandwidth is relatively low.